Intramuscular Nerves of the Inferior Rectus Muscle: Distribution and Characteristics

Hyun Jin Shin, Shin Hyo Lee, Tae Jun Ha, Wu Chul Song, Andrew G. Lee, Ki Seok Koh

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Purpose: Knowledge of the distribution of intramuscular nerves of the extraocular muscles is crucial for understanding their function. The purpose of this study was to elucidate the intramuscular distribution of the oculomotor nerve within the inferior rectus muscle (IRM) using Sihler’s staining. Method: Ninety-three IRM from 50 formalin-embalmed cadavers were investigated. The IRM including its branches of the oculomotor nerve was finely dissected from its origin to the point where it inserted into the sclera. The intramuscular nerve course was investigated after performing Sihler’s whole-mount nerve staining technique that stains the nerves while rendering other soft tissues either translucent or transparent. Results: The oculomotor nerve enters the IRM around the distal one-fourth of the muscle and then divides into multiple smaller branches. The intramuscular nerve course finishes around the distal three-fifth of the IRM in gross observations. The types of branching patterns of the IRM could be divided into two subcategories based on whether or not topographic segregation was present: (1) no significant compartmental segregation (55.9% of cases) and (2) a several-zone pattern with possible segregation (44.1% of cases). Possible compartmentalization was less clear for the IRM, which contained overlapping mixed branches between different trunks. Conclusion: Sihler’s staining is a useful technique for visualizing the gross nerve distribution of the IRM. The new information about the nerve distribution and morphological features provided by this study will improve the understanding of the biomechanics of the IRM, and could be useful for strabismus surgery.

Original languageEnglish (US)
Pages (from-to)1598-1603
Number of pages6
JournalCurrent Eye Research
Issue number12
StateE-pub ahead of print - Jun 18 2020


  • Inferior rectus muscle
  • botulinum toxin injections
  • intramuscular nerve distribution
  • oculomotor nerve
  • sihler’s stain

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems
  • Cellular and Molecular Neuroscience


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